In Antiquity and the Middle Ages music was a mathematical discipline that considered musical proportions the model of ordered movement. With this, music transcended the realm of sound. Thus musica mundana reflected the pattern of planetary motion in the heavens, the balanced distribution of the elements and the orderly seasonal cycle. Musica humana expressed the steady symmetry of human soul and body. From the 9th century onwards, the theme of world harmony was incorporated in music theory, a discipline which was then re-invented, and which developed the relations between celestial and earthly music. It did this by, on one hand, finding within the latter the harmonic and mathematical basis of the former, and, on the other, by considering liturgical chant as the most perfect manifestation of harmony. Liturgical chant, which was considered the universal language of the Church and the human way to overcome carnal temptations and to approach God, was regarded as similar to musica humana, which partly entails a new meaning. 'Human music' is the language of the soul, the inner expression of the mind, which ascends to divinity through intellectual illumination. The soul discovers its medium in the voice, which was considered to be the corporeal manifestation of the soul in music treatises ranging from the 9th to 13th centuries.